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POExtra character in decrypted file from java using aes
 

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  1. POExtra character in decrypted file from java using aes
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    <p>I have written code in vb.net to encrypt a file from a memory stream. I also decrypt the file as well as copy the memory stream to a file to assure encryption/ decryption works. My vb solution works.</p> <p>However my need is to decrypt using Java. When I decrypt my file, I always get an extra "?" character at the very beginning of the file, but other than that the resullts are perfect. Has anyone seen anything like this before? I must admit, my results are from using only one set of data, but I've encrypted it twice using new keys and vectors both times.</p> <p>A few details. I'm using AES, PKCS7 padding in vb, and PKCS5 padding in Java. The file can be of arbitrary length. Any help is appreciated.</p> <p>I am posting this from my phone, and don't have the code handy. I can add it tomorrow. I'm just hoping that this description rings a bell with someone.</p> <p>Thanks, SH</p> <p>When I wrote to the MemoryStream in VB, I declared a StreamWriter like so:</p> <pre><code>Writer = New IO.StreamWriter(MS, System.Text.Encoding.UTF8) </code></pre> <p>Here's my VB.NET encryption function.</p> <pre><code> Public Shared Function WriteEncryptedFile(ms As MemoryStream, FileName As String) As List(Of Byte()) Try Dim original() As Byte Dim myAes As System.Security.Cryptography.Aes = Aes.Create() myAes.KeySize = 128 myAes.Padding = PadMode Dim keys As New List(Of Byte()) keys.Add(myAes.Key) keys.Add(myAes.IV) original = ms.ToArray Dim encryptor As ICryptoTransform = myAes.CreateEncryptor(myAes.Key, myAes.IV) Using FileEncrypt As New FileStream(FileName, FileMode.Create, FileAccess.Write) Using csEncrypt As New CryptoStream(FileEncrypt, encryptor, CryptoStreamMode.Write) csEncrypt.Write(original, 0, original.Length) csEncrypt.FlushFinalBlock() FileEncrypt.Flush() FileEncrypt.Close() csEncrypt.Close() End Using End Using Return keys Catch e As Exception MsgBox("Error during encryption." &amp; vbCrLf &amp; e.Message) End Try Return Nothing End Function </code></pre> <p>And here's the Java decryption:</p> <pre><code>public static void DecryptLIGGGHTSInputFile(String fileIn, String fileOut, String base64Key, String base64IV) throws Exception { // Get the keys from base64 text byte[] key = Base64.decodeBase64(base64Key); byte[] iv= Base64.decodeBase64(base64IV); // Read fileIn into a byte[] int len = (int)(new File(fileIn).length()); byte[] cipherText = new byte[len]; FileInputStream bs = new FileInputStream(fileIn); bs.read(cipherText, 1, len-1); System.out.println(cipherText.length); System.out.println((double)cipherText.length/128); bs.close(); // Create an Aes object // with the specified key and IV. Cipher cipher = null; cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); // Encrypt the message. SecretKey secret = new SecretKeySpec(key, "AES"); /* cipher.init(Cipher.ENCRYPT_MODE, secret, ivspec); cipherText = cipher.doFinal("Hello, World!".getBytes("UTF-8")); System.out.println(cipherText); */ cipher.init(Cipher.DECRYPT_MODE, secret , new IvParameterSpec(iv)); String plaintext = new String(cipher.doFinal(cipherText), "UTF-8"); System.out.println(plaintext.length()); FileWriter fw = new FileWriter(fileOut); fw.write(plaintext); fw.close(); } </code></pre>
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    1. USSuperhuman
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    1. COWhat kind of file is this? Could it be a Unicode BOM?
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      1. USThilo
    2. CONo, it is a simple text file. The text was putthe into thethe memory stream encoded as UTF-8 and when decrypted the bytes were converted back to strings the same way. I should have mentioned the encoding earlier, thanks for the question.
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      1. USSuperhuman
    3. COFor better help sooner, post your code as an [SSCCE](http://www.sscce.org) that demonstrates your problem. This allows users to copy/paste and reproduce your issue.
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      1. USDuncan Jones
 

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